Variable stiffness catheter

ABSTRACT

A variable stiffness catheter having two concentric coils. A first coil is fixed with relation to the body of the catheter and a second coil is able to rotate in the space between adjacent turns of the first coil. The second coil translates axially in response to being rotated. When the second coil is advanced to its distal position, the stiffness is maximized. When the second coil is retracted proximally, the stiffness of the coil is reduced.

RELATED APPLICATIONS

The present patent document is a continuation of application Ser. No.14/207,294, filed Mar. 12, 2014, which claims the benefit of the filingdate under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Ser.No. 61/777,447 filed Mar. 12, 2013, which is hereby incorporated byreference.

FIELD

Embodiments of the present invention generally relate to medical devicesand more particularly to wire guides and catheters for use in peripheralintervention.

BACKGROUND

Wire guides are commonly used in vascular procedures, such asangioplasty procedures, diagnostic and interventional procedures,percutaneous access procedures, and radiological and neurologicalprocedures. In general, wire guides may be used to introduce a widevariety of medical devices into the vascular system.

Generally, during each of the foregoing procedures, a wire guide isfirst inserted into a patient's vascular system and is then advancedtoward a target site. Various wire guides comprise flexible distalregions to facilitate navigation through the tortuous anatomy of apatient's vasculature. Where such flexible distal regions are used, itmay be difficult to insert a medical component over the wire guidebecause of the flexibility of the distal region. However, if the distalregion is too stiff, then it may be too difficult to advance the wireguide to the target site.

In order to facilitate advancement of medical component to the targetsite, some medical procedures utilize two wire guides, a first flexiblewire guide for initially traversing the vasculature, and then a stifferwire guide is advanced over or along the side of the initial wire guide.Once the stiffer wire guide is in place, a catheter can then be advancedover the stiffer wire guide. This procedure works well, but requiresthree different components be advanced through the vasculature of thepatient.

It would be beneficial to have a single component that could function asboth a wire guide and a catheter, such that a single procedure could beused to guide a catheter to a target area. Such a component would needto be flexible to navigate the tortuous anatomy of a patient, yet wouldalso need to be stiff to facilitate pushability of the component.

SUMMARY

In one embodiment of the invention a variable stiffness cathetercomprises an outer layer, an inner layer, a first coil, and a secondcoil. The outer layer has a bore with an inner surface and the innerlayer is disposed within the bore. The inner layer is coaxial with theouter layer and has an outer surface. The first coil has a first helicalaxis coaxial with the inner layer and comprises a first wire wrappedaround the first helical axis in a first plurality of turns disposedbetween the inner surface and the outer surface. The first coil is fixedin place relative to the outer layer and the inner layer. The secondcoil has a second helical axis coaxial with the inner layer andcomprises a second wire wrapped around the second helical axis in asecond plurality of turns disposed between the first inner surface andthe second inner surface. The second plurality of turns are disposedbetween the first plurality of turns and the second coil is rotatableabout the second helical axis relative to the outer layer, the innerlayer, and the first coil.

In another embodiment a variable stiffness catheter comprises a wall, afirst coil, a helical channel in the wall, and a second coil. The wallhas an inner surface and an outer surface and the first coil is disposedin the wall between the inner surface and the outer surface. The firstcoil is fixed in place relative to the wall. The helical channel isdisposed in the wall between the inner surface and the outer surfacebetween adjacent turns of the first coil and the second coil is disposedin the helical channel.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of theone or more present inventions, reference to specific embodimentsthereof are illustrated in the appended drawings. The drawings depictonly typical embodiments and are therefore not to be consideredlimiting. One or more embodiments will be described and explained withadditional specificity and detail through the use of the accompanyingdrawings in which:

FIG. 1 is a side view of the distal end of variable stiffness catheter.

FIG. 2 is a longitudinal cross section of the distal end of the variablestiffness catheter of FIG. 1.

FIG. 3 is a side view of the distal end of a first coil.

FIG. 4 is a side view of the distal end of a second coil.

FIG. 5 is a longitudinal cross section of the distal end of the variablestiffness catheter of FIG. 1 with the second coil moved axially.

FIG. 6 is a longitudinal cross section of the distal end of a variablestiffness catheter having a tube proximal to the second coil.

FIG. 7 is a side view of an embodiment of the first coil having alateral bias at the distal end.

The drawings are not necessarily to scale.

DETAILED DESCRIPTION

As used herein, “at least one,” “one or more,” and “and/or” areopen-ended expressions that are both conjunctive and disjunctive inoperation. For example, each of the expressions “at least one of A, Band C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “oneor more of A, B, or C” and “A, B, and/or C” means A alone, B alone, Calone, A and B together, A and C together, B and C together, or A, B andC together.

Various embodiments of the present inventions are set forth in theattached figures and in the Detailed Description as provided herein andas embodied by the claims. It should be understood, however, that thisDetailed Description does not contain all of the aspects and embodimentsof the one or more present inventions, is not meant to be limiting orrestrictive in any manner, and that the invention(s) as disclosed hereinis/are and will be understood by those of ordinary skill in the art toencompass obvious improvements and modifications thereto.

Additional advantages of the present invention will become readilyapparent from the following discussion, particularly when taken togetherwith the accompanying drawings.

In the following discussion, the terms “distal” and “proximal” will beused to describe the opposing axial ends of the inventive ballooncatheter, as well as the axial ends of various component features. Theterm “distal” is used in its conventional sense to refer to the end ofthe apparatus (or component thereof) that is furthest from the operatorduring use of the apparatus. The term “proximal” is used in itsconventional sense to refer to the end of the apparatus (or componentthereof) that is closest to the operator during use. For example, acatheter may have a distal end and a proximal end, with the proximal enddesignating the end closest to the operator heart during an operation,such as a handle, and the distal end designating an opposite end of thecatheter, such as treatment tip. Similarly, the term “distally” refersto a direction that is generally away from the operator along theapparatus during use and the term “proximally” refers to a directionthat is generally toward the operator along the apparatus.

FIG. 1 illustrates a side view of a distal end 102 of a variablestiffness catheter 100. FIG. 2 is a cross-sectional view of the variablestiffness catheter 100 of FIG. 1. The variable stiffness catheter 100 iscomprised of an outer layer 104, an inner layer 106, a first coil 108,and a second coil 110.

The outer layer 104 has an outer surface 112 and an inner surface 114defining a bore. The inner layer 106 is disposed within the bore of theouter layer 104 and is coaxial with the outer layer 104. The inner layer106 has an outer surface 116 and an inner surface 118 defining a bore ofthe variable stiffness catheter 100. The outer surface 116 of the innerlayer 106 faces the inner surface 114 of the outer layer 104.

FIG. 3 is a side view of the first coil 108. The first coil 108 iscomprised of a first wire 120 wound into a first helix 300 about a firsthelical axis 306. The first helix 300 has a plurality of turns 302having a gap 304 between adjacent turns 302. Each turn 302 of the firsthelix 300 is separated by a pitch 308 distance. The first wire 120 has across section 310 defined by a plane cutting through the first wire 120perpendicular to its axis. In the example of FIG. 3 the cross section310 is a circle, although other patterns are possible. In otherembodiments the cross section 310 may be rectangular, square, or othershape. In some embodiments the cross section 310 may vary along thelength of the wire. The first wire 120 may be comprised of stainlesssteel, although other materials such as nickel titanium alloys and stiffpolymers are suitable for use as the wire.

Returning to FIG. 2, the first coil 108 is disposed between the innersurface 114 of the outer layer 104 and the outer surface 116 of theinner layer 106. The first coil 108 is fixed in place relative to theouter cylindrical layer 104 and the inner cylindrical layer 106. In someembodiments the first coil 108 may be bonded to the inner surface 114 ofthe outer layer 104 and the outer surface 116 of the inner layer 106 tofix the first coil 108 in place.

FIG. 4 is a side view of the second coil 110. The second coil 110 iscomprised of a second wire 122 wound into a helix 400 about a secondhelical axis 402. The second coil 110 has a pitch 408 that issubstantially the same as the pitch 308 of the first coil 108, such thatthe second wire 122 may be disposed in the gap 304 between adjacentturns 302 of the first coil 108 without interfering with the first wire120. The second coil 110 is disposed between the inner surface 114 ofthe outer layer 104 and the outer surface 116 of the inner layer 106with the second wire 122 lying in the gap 304 between adjacent turns 304of the first coil 108. The second coil 110 is not fixed relative to theouter layer 104 and the inner layer 106 and is constrained in movementby the first wire 108, the outer layer 104, and the inner layer 106.

The second coil 110 is rotatable about the second helical axis 402relative to the outer layer 104, the inner layer 106, and the first coil108. Like a screw, when the second coil 110 rotates about the secondhelical axis 402, the second coil 110 translates axially relative to thefirst coil 108. Rotating the second coil 110 in a first direction willcause the second coil 110 to translate distally, while rotation of thesecond coil 110 in the opposite direction will cause the second coil 110to translate proximally.

The second wire 122 may have a second cross section 406 that issubstantially the same as the first cross section 306 as shown in FIG.4. In other embodiments, the cross section 406 of the second wire 122 isshorter in a radial direction than the cross section 306 of the firstwire 120. Having a shorter cross section 406 reduces the resistance torotation of the second coil 110 relative to the inner surface 114 of theouter layer 104 and the outer surface 116 of the inner layer 106. Thesecond wire 122 may be comprised of stainless steel, although othermaterials such as nickel titanium alloys and stiff polymers. In someembodiments, the second wire 122 may comprise a different material thanthe first wire 120. For example, the first wire 120 could be comprisedof a nickel titanium alloy and the second wire 122 could be comprised ofstainless steel.

The variable stiffness catheter 100 has a stiffness along its lengththat is equal to the combined stiffness of the inner layer 106, theouter layer 104, the first coil 108, and the second coil 110. When thesecond coil 110 is moved proximally through the rotation of the secondcoil 110, a region of reduced stiffness is present in the region distalto the distal end 410 of the second coil 110. Thus, when the second coil110 is retracted proximally, the variable stiffness catheter 100 has afirst region 502 proximal to the distal end 410 of the second coil 110having a higher stiffness and a second region 500 distal to the distalend 410 of the second coil 110 having a lower stiffness, as shown inFIG. 5.

FIG. 5 shows a longitudinal cross section of the distal end 102 of thevariable stiffness catheter 100 with the second coil 110 being displacedproximally relative to the first coil 108. The second region 500 of thevariable stiffness catheter 100 can be lengthened by further moving thedistal end 410 of the second coil 110 distally. Similarly, the length ofthe second region 500 can be increased by moving the distal end 410 ofthe second coil 110 distally. For example, it may be useful to have aflexible tip when traversing a tortuous vascular system, and then switchto a more rigid tip once past the tortuous vascular system. This wouldbe accomplished by moving the distal end 410 of the second coil 110proximally for use when traversing the tortuous vascular system and thenadvancing the distal end 410 of the second coil 110 once past thetortuous vascular system.

FIG. 6 illustrates another embodiment of a variable stiffness catheter600. This embodiment is similar to the previously described embodimentof FIG. 1 and is comprised of an outer layer 602, an inner layer 604, afirst coil 606, a second coil 608, and a tube 610. A distal and 618 ofthe tube 610 is coupled to a proximal end 615 of the second coil 608. Inthe embodiment of FIG. 6, the tube 610 has an outside diameter 614greater than an inside diameter 616 of the first coil 606. To avoidinterference between the first coil 606 and the tube 610, first coil 606ends prior to the distal end 618 of the tube 610. In other embodiments,the tube 610 may have an outside diameter 614 less than the insidediameter 616 of the first coil 606 such that the tube 610 is able topass within the first coil 606. The tube 610 has a greater torsionalstiffness than the second coil 608 and is used to transmit torque over agreater distance than the second coil 608 alone. The proximal end (notshown) of the tube 610 is disposed proximate the proximal end of thevariable stiffness catheter 600 and transmits relative rotation of thetube 610 near the proximal end of the variable length catheter 600 tothe second coil 608 disposed at the distal end of the variable lengthcatheter 600. The tube 610 may be comprised of stainless steel, althoughother materials such as nickel titanium alloys and stiff polymers aresuitable for use as the tube.

FIG. 7 illustrates a longitudinal cross section of an alternativeembodiment of the first coil 700. In this embodiment the first coil 700is self-biased to have a lateral displacement 702 at its distal end 704.The second coil is biased to be substantially straight. When the distalend of the second coil is proximate the distal end 704 of the first coil700, the variable stiffness catheter 100 is substantially straight. Asthe second coil is retracted proximally, the bias of the first coil 700causes the distal end of the variable stiffness catheter 100 to deflectin the direction of the bias. This allows the variable stiffnesscatheter 100 to have a variable curve depending on the needs of theuser.

In some embodiments, as partially shown in FIG. 5, the inner surface 114of the outer layer 104 may extend into the gap between adjacent turns ofthe first coil 108. In such embodiments the inner surface 114 of theouter layer 104 may have a helical groove 550 in the gap for receivingthe second coil 110. In other embodiments, the outer surface of theinner layer 106 may extend into the gap between adjacent coils of thefirst coil 108. In such embodiments, the inner layer 106 may have ahelical groove 552 in the gap for receiving the second coil 110.

In another embodiment the inner layer and the outer layer may becomprised of the same material and form an integral wall having thecoils disposed within the wall. In such embodiments the first coil isfixed within the wall and the second coil is free to rotate relative tothe first coil and the integral wall. The helical channel is formed inthe integral wall in the gap between adjacent turns of the first coil.The second coil travels in the helical channel when rotated relative tothe first coil and the integral wall. The channel may be formed bycoating the second coil with a release compound allowing the integralwall to be formed with the second wire in place. Because the second coilis coated with the release compound it may be rotated within theintegral wall since it is not adhered to the integral wall lie the firstcoil.

In some embodiments a helical plug having a cross section larger thanthe second coil may be coated with a release compound when the integralwall is formed. The helical plug may then be removed leaving a channelhaving a cross section greater than the second coil. The second coil maythen be threaded into the helical channel left by the helical plug.

Embodiments of the invention have been primarily described in terms of asingle lumen catheter. It should be understood that various changes andmodifications to the presently preferred embodiments described hereinwill be apparent to those skilled in the art. Such changes andmodifications can be made without departing from the spirit and scope ofthe present invention and without diminishing its intended advantages.It is therefore intended that such changes and modifications be coveredby the appended claims.

What is claimed:
 1. A method of varying the stiffness of a catheter,comprising: guiding a distal end of a variable stiffness catheter to atarget location, the variable stiffness catheter comprising an outerlayer, an inner layer disposed within the outer layer and being coaxialwith the outer layer, a first coil comprising a first wire wrappedaround the inner layer, and a second coil comprising a second wirewrapped the inner layer between turns of the first coil; and rotatingthe second coil causing the second coil to move axially between theinner and outer layer, thereby changing the stiffness at the distal endof the variable stiffness catheter.
 2. The method of claim 1, whereinthe rotation of the second coil causes the distal end of the second coilto move distally, thereby increasing the stiffness of the catheter atthe distal end.
 3. The method of claim 2, wherein the distal end of thevariable stiffness catheter is guided through a tortuous vascular systemto the target area with the second coil in a retracted state, andwherein the method further comprises guiding the distal end of thevariable stiffness catheter to a second target location after increasingthe stiffness of the catheter at the distal end.
 4. The method of claim1, wherein the rotation of the second coil causes the distal end of thesecond coil to move proximally, thereby decreasing the stiffness of thevariable stiffness catheter at the distal end.
 5. A method of guiding avariable stiffness catheter through a vascular system, comprising:advancing a distal end of a variable stiffness catheter within avascular system, the variable stiffness catheter comprising an outerlayer, an inner layer disposed within the outer layer and being coaxialwith the outer layer, a first coil self-biased to have a lateraldisplacement at a distal end, the first coil comprising a first wirewrapped around the inner layer, and a second coil comprising a secondwire wrapped the inner layer between turns of the first coil, the secondcoil being self-biased to a straight configuration; encountering a turnwithin the vascular system; and rotating the second coil causing thedistal end of the second coil to retract relative to the distal end ofthe first coil and allowing the self-bias of the first coil to deflectlaterally.
 6. The method of claim 5, further comprising: advancing thedistal end of the variable stiffness catheter into the turn with thelaterally deflected first coil; and encountering a straight portionwithin the vascular system; and rotating the second coil causing thedistal end of the second coil to advance relative to the distal end ofthe first coil and overcoming the self-bias of the first coil to returnthe distal end of the variable stiffness catheter to a straightconfiguration.